A secondary battery has high applicability depending on the product group and excellent electrical characteristics such as high energy density, and thus is commonly used as an electric power source of electric vehicles (EV) or hybrid vehicles (HV) as well as mobile devices.
Such a secondary battery can be repetitively charged and discharged by an electrochemical reaction, so to not only significantly reduce the use of fossil fuels but also generate any by-products that come with energy consumption. Therefore, secondary batteries improve energy efficiency, are environmentally friendly, and are gaining attention as a new alternative energy source.
A battery pack, which is used in electric vehicles, conventionally includes an assembly, consisting of a plurality of unit cells, and a plurality of assemblies or battery modules. The cell includes a cathode current collector, a separator, an active material, an electrolyte solution, an aluminum thin film layer, etc., and has a structure capable of charging or discharging by an electrochemical reaction between components.
Meanwhile, an individual secondary battery is referred to as a cell, a group of secondary batteries is referred to as an assembly (i.e., battery module), and a group of assemblies is referred to as a battery pack. Unless otherwise mentioned herein, the term ‘a secondary battery’ which is used herein is defined not only as a cell, but also as a battery assembly or a battery pack, and the term ‘a battery pack’ which is used herein is defined as a group consisting of a plurality of secondary batteries.
Recently, with the increasing significance of global issues relating to the exhaustion of energy resources such as fossil fuels, environmental pollution, economically efficient energy use, and the like, a smart grid system has been actively studied to effectively overcome the inequality in power consumption and power production and solve the problems caused thereby, such as, power wastage when power is oversupplied and power overload when power supply is in shortage. The smart grid system flexibly controls the power supply using a variety of information and communication infrastructures.
In other words, the infrastructure of a smart grid system is configured to store surplus power when power consumption is low and supply the stored power with supply power to consumers when power consumption is high.
In this instance, the smart grid system needs a medium for storing power. As such a medium, a secondary battery or a battery pack is dominantly used.
Also, a power storage battery pack can be used in other various fields besides the smart grid system. For example, since an electric vehicle charging station which is designed to supply electric power to electric vehicles by charging requires a large amount of power to be stored, a power storage battery pack may also be used for the electric vehicle charging station.
The power storage battery pack is implemented as a large-capacity system by assembling a plurality of secondary batteries in various structures (e.g, a tower-shaped stack in which battery packs are vertically stacked), and the secondary batteries are repetitively charged and discharged by electrochemical reactions. This repeated charging or discharging inevitably generates heat in the secondary batteries, and the heat dramatically increases with increasing battery capacity.
However, such heat may cause potential injury or damage to a secondary battery allowing electrochemical reactions, resulting in deterioration in the performance of the battery, which may not ensure the life of the battery. Furthermore, heat is also known as a fatal factor exerting a bad influence on the safety of the battery, which may cause explosion and the like.
Accordingly, a secondary battery needs a cooling system to remove heat generated during operation. Particularly, in the case of a high-capacity high-integration power storage system, a cooling system is even more necessary to solve the heat generation problem.
However, a conventional system for cooling a power storage battery pack is obtained by simply combining a plurality of systems which cool an individual battery pack, and fails to optimize power storage battery packs accumulated in a large-scale.
In the case of the conventional system, since each battery pack in a tower-shaped stack needs to be independently operated by means of an individual cooling control method, there occurs an inefficiency in that a duplication of cooling systems occur. Furthermore, since a battery management system (BMS) for controlling an individual battery pack and logics for driving the BMS are required, it may cause a complexity in an air conditioning system which is significantly inefficient in terms of the management of the cooling system, including maintenance or repair.
Also, unlike a battery pack installed in vehicles, a conventional power storage battery pack and a cooling system thereof may occasionally be installed outside a facility which may incidentally damage the insulating property of the battery pack by water permeation.